Hereinafter, a machine-to-machine communication environment in the present invention will be described in brief.
Machine-to-machine (M2M) communication refers to communication between electronic devices as the name implies. In a broad sense, M2M communication means wired or wireless communication between electronic devices or communication between a device controlled by humans and a machine. Recently, M2M communication generally refers to wireless communication between electronic devices without human intervention.
In the early 1990s when the concept of M2M communication was first introduced, M2M communication was recognized as remote control or telematics and the market therefor was very limited. However, M2M communication has rapidly advanced in the past few years and the market therefor has vastly expanded, attracting worldwide attention. In particular, M2M communication has exerted a significant influence on the fields of fleet management in a point-of-sale (POS) system and security-related application markets, remote monitoring of machines and facilities, and smart metering of measuring operating time of construction equipment and automatically measuring heat or electricity use. Future M2M communication will be extended to various applications in association with existing mobile communication, ultra-fast wireless Internet, or low-output communication solutions such as Wi-Fi and ZigBee. That is, M2M communication will evolve from a business-to-business (B2B) application to a business-to-consumer (B2C) model.
In an era of M2M communication, all machines equipped with a subscriber identity module (SIM) card are able to transmit and receive data so that they can be remotely managed and controlled. For example, M2M communication technology may be used in a wide range of devices and equipment such as automobiles, trucks, trains, shipping containers, vending machines, gas tankers, etc.
Conventionally, terminals were managed individually for one-to-one communication between a base station (BS) and a terminal Assuming that numerous M2M devices communicate with the BS through one-to-one communication, network overload is likely to occur due to signaling generated between each of the M2M devices and the BS. As M2M communication rapidly spreads and expands, overhead may be problematic due to communication between the M2M devices or between the M2M devices and a BS.
Further, since a human does not participate in operations of M2M devices in an M2M system, an abnormal/involuntary power outage event may occur in the M2M devices. Such power outage may also occur in most M2M devices in a region to which the M2M devices of a power outage state belong.
If an involuntary power outage event occurs, M2M devices should report the power outage event to the BS. For example, M2M devices in an idle-mode state will perform a ranging procedure in order to report the power outage event and then collision may occur between M2M devices. Moreover, M2M devices in a normal-normal state will perform a bandwidth request procedure to report the power outage event and then there is a high possibility of collision between M2M devices.
If collision occurs between M2M devices, the M2M devices perform a collision resolution procedure. In this case, if the M2M devices perform random access by applying an initial backoff window size defined for network re-entry to existing terminals in normal mode and normal terminals, a probability of collision between the M2M devices and normal terminals increases and power outage reporting may be delayed.
In addition, such a random access procedure may consume unnecessary power in M2M devices and deteriorate efficiency of system resource use. Furthermore, if an additional ranging channel for M2M devices is not used in a system, the random access procedure may affect even a random access procedure for existing terminals.